Mortising apparatus



Jan. 27, 1970 H. N. BUTLER MORTISING APPARATUS 3 Sheets-s 1 File 'Spt 8' 1967 INVENTOR HowARb N. BUTLER ATTORNEYS Jan. 27, 1970' H. N. BUTLER MORTISING APPARATUS Filed Sept. 8, 1967 3 Sheets-Sheet 2 H NINgENTOR OWARb uTLE-R BYMJEZk/Jfagfiljf 45m ATTORNEYS Jan. 27, 1970 H. N. BUTLER MOR'IISING APPARATUS 3 Sheets-Sheet 8 Filed Sept. 8, 1967 119115 INVENTOR: 55 HOWARB N BUTLER.

ATTORNEY$ United States Patent 3,491,812 MORTISING APPARATUS Howard N. Butler, Box 89, Southern Pines, N.C. 28387 Filed Sept. 8, 1967, Ser. N0. 669,640 Int. Cl. B27f /02 us. c1. 144 7s 11 Claims ABSTRACT OF THE DISCLOSURE One of the classic types of fence which have been widely used in this country from early pioneer days to the present time is known as post and rail fence, and uses vertical posts set into the ground and horizontal rails wedged into elongate mortises formed in the posts. The posts of such a fence are provided with elongate mortises having a generally rectangular, rounded end outline configuration, while the rails have tapered ends so that a pair of rails may be secured to a post at each post mortise, by wedging engagement therewithin.

Heretofore, the manufacture of posts for a post and rail fence has entailed particular difliculty in the formation of the elongate mortises for receiving the rails. The classic method of forming such mortises involves boring, with a hand anger or wood bit, a first hole through a wooden fence post and then a second hole partially overlapping with the first hole. The figure eight elongate mortise thus formed is then trimmed out to a generally rectangular, rounded end, outline configuration by chiseling out, by hand, the generally triangular cusps of wood which lie outside, immediately adjacent and between the overlapping bores of the two holes. It is apparent that substantial hand labor is involved in such manufacture of fence posts for post and rail fences, but such an expenditure of time and manual labor was entirely acceptable in a less mechanized age.

At the present time, conditions are such that an expenditure of time and labor such ase would be necessary to manually form elongate mortises in fence posts is not economically feasible. Recognizing this, persons desirous of obtaining post and rail fencing must either buy antique fencing or accept the commercially available mechanically manufactured substitutes for the classical post and rail fence. Such commercially available substitutes suffer from deficiencies due to the expedients adopted to permit assembly of the fences. For example, certain fences employ steel dowel pins, which penetrate a fence post and extend into the ends of the fence rails. In such a fence, the rails may rotate relative to the posts and, as a result, adjacent posts do not lend support to one another in the event that force is applied to the rails, as when an animal confined within the fence leans against the fence. With the above discussion in mind, it is an object of the present invention to provide an apparatus for forming elongate mortises in splittable materials such as wood and the like, wherein the mortise formed by the apparatus has a generally rectangular, rounded end, outline configuration and generally is identical in appearance with a mortise formed by the manual technique previously employed in producing posts for post and rail fences. In realizing this object of this invention, means are provided for boring a pair of overlapping holes through a wooden workpiece and for splitting triangular cusps of material from the workpiece adjacent the overlapping bores. While such operations were performed sequentially in accordance with previously employed manual techniques, the apparatus of the present invention performs such operations at least substantially simultaneously to realize a substantial saving in time, and is particularly adapted for power operation.

A further object of the present invention is to provide an apparatus for mortising elongate splittable material workpieces such as wooden fence posts, wherein means are provided for receiving and supporting a workpiece while a plurality of elongate mortises having generally rectangular, rounded end, outline configurations are formed therein at predetermined spaced apart locations. In realizing this object of the present invention, and apparatus is provided which performs, in a single operation, all steps required to convert a length of log into a fence post prepared for installation in a classical post and rail fence.

Some of the objects and advantages of the invention having been stated, others will appear as the description proceeds, when taken in connection with the accompanying drawings, in which FIGURE 1 is a perspective view of an apparatus for mortising and elongate splittable material workpiece, in accordance with the present invention;

FIGURE 2 is a perspective view of one type of workpiece, as mortised by the apparatus of FIGURE 1;

FIGURE 3 is a view similar to FIGURE 2 of a second type of workpiece, as mortised by the apparatus of FIG- URE 1;

FIGURE 4 is a schematic illustration of certain elements of the apparatus of FIGURE 1, illustrating locking of a workpiece into position for mortising;

FIGURE 5 is a view similar to FIGURE 4 of certain portions of the apparatus of FIGURE 1, illustrating the ejection of a workpiece subsequent to the mortising thereof;

FIGURE 6 is a enlarged elevation view, in partial section, of portions of the apparatus of FIGURE 1, illustrating the manner in which a workpiece is supported for mortising;

FIGURE 7 is a view similar to FIGURES 5 and 6, illustrating certain portions of the apparatus of FIG- URE l which are involved in the ejection of a workpiece subsequent to mortising;

FIGURE 8 is a view similar to FIGURE 7, illustrating the accomodation of the apparatus of FIGURE 1 to a workpiece of the type shown in FIGURE 3;

FIGURE 9 is an end elevation view of a mortise cutting head employed in the apparatus of FIGURE 1;

FIGURE 10 is a side elevation view of the mortise cutting head of FIGURE 9, partly broken away;

FIGURE 11 is a view from below of the mortise cut ting head of FIGURES 9 and 10, illustrating the directions of rotation and a predetermined phase relationship of boring bits incorporated therein;

FIGURE 12 is an enlarged scale detail of an operative connection of the boring bits of FIGURES 9 through 11; and

FIGURE 13 is a view of an elongate mortise as formed by the mortising h ad of FIGURES 9 through 12.

Referring now more particularly to the drawings, in apparatus for forming elongate mortises in splittable materials such as wood and the like as comprehended by the present invention is incorporated within an apparatus for mortising an elongate splittable material workpiece such as wooden fence posts, which workpiece mortising apparatus is generally indicated at 20 (FIGURE 1). The apparatus 20 comprises an elongate workpiece supporting frame 21 and an elongate mortising head frame 22 which is normally positioned in predetermined spaced relation above the workpiece supporting frame 21, as brought out more fully hereinafter. Actuation means are provided for displacing one of the frames 21, 22 relative to the other of the frames, in order to result in the mortising of an elongate splittable material workpiece such as a wooden fence post.

More particularly, the workpiece supporting frame 21 is constructed with pairs of vertically spaced apart lower channel members 24 and 25 and upper channel members 26 and 27. The channel members 24-27 are secured to four standards 30, 31, 32 and 33, and in turn support a pair of fore and aft vertical standards 35 and 36 on pairs of cross-brace channel members 38, 39, 40 and 41. The upper extremities of the standards 35 and 36 are connected by longitudinal stringer members 42 and 43. The workpiece supporting frame 21 further includes cradle means for receiving an elongate workpiece with thelongitudinal axis thereof in a predetermined orientation relative to the supporting frame 21. Preferably, the cradle means includes a pair of longitudinally spaced apart bench members 45 and 46, secured to the upper channel members 26 and 27 of the workpiece supporting frame 21 (FIGURES 1 and 4-8). The bench members 45 and 46 are configured with a V-notch or V-slope shape, with the lowest points of the V spaced approximately halfway between the channel members 26 and 27 and in longitudinal alignment, to position a workpiece with the longitudinal axis thereof generally parallel with the longitudinal axes of the elongate frame members 24-27. The mortising head frame 22 preferably includes a pair of longitudinal channel members 50 and 51, which engage the standards 35 and 36 to be guided thereby in vertical movement relative to the workpiece supporting frame 21. Vertical movement of the mortising head frame 22 relative to the workpiece supporting frame 21 is governed by three pressure fluid cylinder members 54, 55 and 56, which suspend the mortising head frame 22 from the longitudinal stringer members 42 and 43 of the workpiece supporting frame 21. Depending upon the application of pressure fluids to the cylinders 54, 55 and 56 under the control of an appropriate pressure fluid valve 57, the mortising head frame 22 is displaceable downwardly and upwardly along a path of travel determined by the vertical standards 35 and 36 and toward and away from the cradle means defined by the bench members 45 and 46.

Mounted on the mortising head frame 22 for adjustable positioning along the channel members 50 and 51 are a plurality of mortise cutting heads 60, 60' and 60", for forming a corresponding plurality of spaced apart mortises in a workpiece upon engagement therewith as the mortising frame 22 moves downwardly toward the cradle means. Each of the mortising heads, for example the mortising head 60, comprises a frame 61 constructed for attachment to the channel members 50 and 51 of the mortising head frame 22. The frame 61 serves to mount a pair of wood boring bits 62 and 63 for rotation about the longitudinal axes of the bits with those longitudinal axes parallel and spaced apart a predetermined distance. Each of the boring bits 62 and 63 has a respective cutting wing portion 65 and 66 of a predetermined radius for describing a circle of a predetermined diameter upon rotation of the corresponding bit about its longitudinal axes. The shank portions of the bits are of reduced radius or diameter relative to the wing portions (FIGURES 9 and The predetermined distance by which the longitudinal axes of the bits 62 and 63 are spaced apart by the frame 61 is less than the sum of the predetermined radii of the wing portions, for purposes to be described more fully hereinafter.

In addition to the frame 61, the means mounting the wood boring bits 62 and 63 includes a pair of stub shafts 70 and 71, ea h of which is fixed to a. spur g a 72 and 73 respectively, and supported in the frame 61 for rotation about a predetermined axis. The lower terminal extremities of the stub shafts 72 and 73 are provided with a. taper threaded socket portion, for receiving a correspondingly taper threaded shank portion of the boring bits 62 and 63 (FIGURE 12). The use of taper threads facilitates securing the boring bits 62 and 63 to the stub shafts 72 and 73 in a predetermined angular relationship, limited by the engagement of locking shoulders adjacent the threaded portions, as is conventional in certain well drilling tool practices. While the tapered thread and locking shoulder arrangement has been adopted in the mortise cutting heads illustrated in the FIGURES 9-12 of the present application, it is to be recognized that other means may be adopted, within the scope comprehended for the present invention, for assuring positioning of the Wing portions of the boring bits 62 and 63 in a predetermined angular relationship so long as such means is capable of locking the bits so securely that the angular relationship is maintained during operation of the apparatus.

By virtue of the securement of the stub shafts 70 and 71 with the spur gears 72 and 73, rotation of the shafts and thus of the boring bits in a predetermined phased relationship is assured. One of the stub shafts, such as the shaft 71, penetrates the respective spur gear 73 and extends beyond the upper surface of the frame 61, to be engaged by an appropriate motive driving means such as an electrical motor M. When driven by the electrical motor M, the bits 62 and 63 are rotated about their longitudinal axes and with the wing portions in predetermined phased relationship so that the boring bits rotate free of interference one with the other while the wing portions describe overlapping circles (FIGURE 11).

In order to remove generally triangular cusps of splittable material lying outside the overlapping bores cut by the bits 62 and 63 and extending toward the area of bore overlap, the mortise cutting head 60 further includes splitting means positioned adjacent the shank portion of the bits 62 and 63. Preferably, the splitting means includes a generally ovoid chisel or knife portion 75 supported by a pair of side plates 76 and 77 which are bolted to the side covers of the frame 61. The knife portion 75 of the splitting means is spaced upwardly from the wing portions of the boring bits (FIGURES 9 and 10) and generally lies within the overlapping circles described by the win-g portions of the boring bits and two straight lines tangent to those circles and joining those circles. It has been found that this position of the chisel portion 75 within lines tangent with the overlapping circles described by the boring bits 62 and 63 results in avoidance of excessive power demands which otherwise occur during splitting of the triangular cusps of material otherwise left in place by the boring bits from the Wooden workpiece. Accordingly, it is preferred that the chisel portion 75 lie within such an outline area rather than along or outside of the circles and lines. In order to facilitate splitting of the cusps of material and removal of the splitt-able material by the counter rotating twisted shanks of the bits 62 and 63, the chisel portion 75 is more sharply pointed and rounded inwardly in the area of the triangular cusp to be split from the splittable matreial workpiece (FIGURES 9-11). Elements of the mortising heads 60' and 60" corresponding to the elements of the mortising head 60 are identified by like prime and double prime notation.

In order to assure that :a workpiece is secured in proper position on the cradle means including the bench members 45 and 46, this invention contemplates the inclusion of controllable means for engaging a workpiece, positioning the workpiece and locking the same in a desired position for mortising. More particularly, a fixed abutment means, in the form of a channel 80 (FIGURES 1 and 4) is positioned in alignment with the location of the longitudinal axes of a workpiece supported 9n the cradle means, and an end c amping mean g nera y indicated at 81 is located at the opposite extremity of the workpiece supporting frame 21. Preferably, the end clamping means 81 comprises a fluid pressure cylinder 82 pivotally connected at one end to a member of the workpiece supporting frame 21 and having a workpiece engaging plate 83 secured to the piston rod 84 thereof. Upon application of suitable fluid pressure to the cylinder 82 under the control of a valve 85, such as air drawn from a suitable source of compressed air, the plate 83 is projected into contact with one endface of a workpiece supported and positioned on the cradle means (indicated in phantom lines in FIGURE 4), to urge the opposite extremity of the workpiece into engagement with the abutment member 80, and thereby positively position the workpiece in a predetermined location relative to the workpiece supporting frame 21.

Further, this invention comprehends the inclusion of side clamping means for engaging a workpiece positioned on the cradle means for assuring that the workpiece is maintained in the desired position throughout the mortising operation. More particularly, a pair of locking yoke members 90 and 91, respectively, are supported on the workpiece supporting frame 21 for pivotal movement between upward withdrawn positions (FIGURE 1) and lowered workpiece engaging positions (FIGURE 4). The movement of the yoke members 90 and 91 between the two extreme positions preferably is controlled by a lock down pressure fluid cylinder 92, operatively connected with the pivotal locking yoke members 90 and 91 through a suitable linkage (FIGURE 4). Upon application of a suitable pressure fluid to the cylinder 92 through a control valve 93, such as compressed air from a suitable source, the locking yoke members 90 and 91 are pivoted from the upward and withdrawn position toward the downward and locked position, to engage the upper side of a workpiece (such as the workpiece W as illustrated in phantom lines in FIGURE 4) and to urge the workpiece downwardly into engagement with the bench members 45 and 46 of the cradle means, and thereby secure the workpiece in a predetermined orientation relative to the supporting frame 21 during the mortising operation.

With a workpiece (such as the workpiece W of FIG- URE 2) secured in position in the cradle means on the workpiece supporting frame 21, electrical energy is applied to the driving motors M of the plurality of mortise cutting heads under the control of appropriate motor switches 94 (FIGURE 1). At the same time, pressure fluid is introduced to the pressure fluid cylinders 54, 55 and 56 which constitute an actuation means for displacing the mortising head frame 22 relative to the workpiece supporting frame 21, and the mortising head frame 22 is moved into closer proximity with the cradle means. The mortising heads 60, 60' and 60" are thus brought into engagement with the workpiece, and are driven through the workpiece simultaneously forming a corresponding plurality of mortises therein, to produce the finished fence post product shown in FIGURE 2. The conformation of the mortises formed by the mortising heads 60, 60' and 60" is illustrated in FIGURE 13, where the overlapping circular bores cut by the boring bit and the splitting removal of the generally triangular cusps extending therebetween have resulted in a generally rectangular, rounded end, outline configuration for the elongate mortise.

' In order to facilitate removal of a finished product workpiece (such as the workpiece W of FIGURE 2) after mortises have been formed therein, this invention further contemplates that a workpiece removal or kickout means by provided. More particularly, a pair of throw out arms 97 and 98 are supported by the workpiece supporting frame 21 for pivotal movement adjacent the bench members 45 and 46 of the cradle means (FIGURE 5) and a suitable pressure fluid cylinder 99 is provided for controlling pivotal movement of the kickout arms 97 and 98. Upon application of appropriate fluid pressure to the kickout actuation cylinder 99 through a control valve 100,

the arms 97 and 98 are pivoted from a retracted position beneath the cradle means to an elevated position (from the solid line position of FIGURE 7 to the dotted line position of FIGURE 7) to lift a workpiece W from the cradle means and discharge the same over the side of the apparatus. In order to assure proper discharge of a completed workpiece W, this invention further provides discharge guards 101 and 102 immediately adjacent the kickout position location of the arms 97 and 98, to receive the workpiece expelled from the workpiece supporting frame 21 and guide the same to fall on an adjacent portion of a factory floor.

In order to avoid excessive splitting of the workpiece W during the formation of mortises therein, this invention further provides a resilient padding means for underlying the workpiece W during the mortising operation. This padding means preferably comprises a spring mounted rigid support member 105 supported on the workpiece supporting frame 21 for vertical movement and urged to an upward position by suitable resilient means such as compression springs 106 (FIGURE 6). Mounted on the rigid member 105 is a semi-resilient block 107 of long wearing material which has an opening therein at least substantially corresponding with the outline configuration of the mortise formed by a mortising head 60. The supporting means is positioned on the workpiece supporting frame 21 to underlie a corresponding mortising head, with the opening in the semi-resilient block 107 aligned with the cutting members of the corresponding mortising head. Upon positioning of a workpiece, such as the workpiece W, in the cradle means of the workpiece supporting frame 21 and engagement thereof with the locking means for securing the workpiece in position for mortising, the workpiece is urged into engagement with the semi-resilient block 107, against the upward urging force of the compression springs 106. Due to the substantial congruency of the elongate mortise formed by the mortising head 60 and the opening in the semi-resilient block 107, splitting of the material of the workpiece W on exit of the boring bits and chisel means of the mortising head from the lower side of the workpiece is avoided, due to the support provided for the splittable material by the semi-resilient block 107.

In order to accommodate workpieces of generally rectilinear cross-sectional configuration, such as the workpiece W of FIGURE 3, this invention further provides for the use of a generally triangular bench adapter 110 (FIGURE 8) which may be positioned on the bench members 45 and 46 of the cradle means to provide a flat surface for receiving a correspondingly flat surface of the workpiece W. Additionally, and in order to assure that the workpiece W is properly located in the predetermined orientation relative to the workpiece supporting frame 21 required for proper formation of mortises in the workpiece W', a blocking member 111, hingedly interconnected with the lifting arms 97 and 98, includes an upward portion which rises above the bench members 45 and 46 when the lifting arms 97 and 98 are in the retracted position to provide a side edge block for locating one side of a square cross-sectional workpiece W (FIGURE 8).

In operation, a workpiece of round or square crosssectional configuration is dropped into position on the cradle means of the workpiece supporting frame 21, and pressure fluid is admitted to the end clamping cylinder 82, to locate the workpiece with one end in abutment with the abutment member and thus in proper longitudinal position in relation to the workpiece supporting frame 21. Fluid pressure is then applied to the side clamping means cylinder 92, to pivot the locking arms and '91 downwardly and engage the yoke members thereof with the workpiece W to urge the same downwardly into engagement with the bench members 45 and 46 and into engagement with the semi-resilient pads 107 of the anti-splintering mechanism. With the workpiece thus positioned in the desired predetermined orientation and secured in place, pressure fluid is admitted to the actuation means cylinders 54, 55 and 56 controlling movement of the mortising head frame 22 relative to the workpiece supporting frame, and electrical current is applied to the motors M driving the boring bits of the mortise cutting heads 60, 60' and 60". Thus, the mortise cutting heads mounted on the mortising frame are brought into engagement with the workpiece as the mortising frame and cradle means move into closer proximity, and the mortising heads form a corresponding plurality of elongate generally rectangular, rounded end mortises in the workpiece locked into position in the workpiece supporting frame 21. Upon completion of formation of the mortises, the application of pressure to the actuation means cylinders controlling displacement of the mortising head frame 22 is reversed to raise the frame 22. The workpiece is then released by reversing the application of fluid pressures to the lock down cylinder 92 and the pushing cylinder 82, and pressure fluid is applied to the lifting arm cylinder 99 to discharge the mortise workpiece from the apparatus. The apparatus is thus prepared for another cycle.

In the drawings and specification, there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.

I claim:

1. Apparatus for mortising elongate splittable material workpieces such as wooden fence posts comprising:

a workpiece supporting frame including cradle means for receiving an elongate workpiece with the longitudinal axis thereof in a predetermined orientation relative to said supporting frame, a mortising head frame normally positioned in predetermined spaced relation to said cradle means,

actuation means for effecting relative movement of said frames toward and away from each other along a predetermined path of travel, and

at least one mortise cutting head mounted on said mortising frame for forming a mortise in a workpiece supported in said cradle means upon engagement therewith as said frames move toward each other, said cutting head comprising:

first and second boring bits having respective cutting wing portions each of a predetermined radius for describing respective circles of predetermined diameters upon rotation of said bits about the longitudinal axes thereof and said bits also having respective shank portions of reduced size relative to said wing portions,

means mounting said first and second bits for rotation with said longitudinal axes thereof parallel and spaced apart a predetermined distance less than the sum of said radii, said mounting means securing said bits with said wing portions in a predetermined angular relationship,

means for driving said first and second bits in rotation about said longitudinal axes thereof and for maintaining a predetermined angular phase relationship between said wing portions so that said first and second bits rotate free of interference one with the other while said wing portions describe overlapping circles, and

means fixed adjacent said shank portions of said bits and including a chisel portion spaced inwardly of said circles described by said boring bit wing portions and lines tangent to and joining said circles for splitting generally triangular cusps lying outside and immediately adjacent overlapping circles described by said bits from a workpiece, said splitting means cooperating with said first and sec-nd bits to form an elongate mortisf; having roundt d ends.

2. Apparatus according to claim 1 further comprising:

workpiece end clamping means mounted on said workpiece supporting frame and operable for engaging the terminal extremities of a workpiece received by said cradle means and for positioning the workpiece relative to said supporting frame.

3. Apparatus according to claim 1 further comprising:

workpiece side clamping means mounted on said workpiece supporting frame and operable for engaging a workpiece and for cooperating with said cradle means for securing the workpiece relative to said supporting frame during the mortising thereof.

4. Apparatus according to claim 3 further comprising:

anti-splintering means for avoiding workpiece splitting around a mortise upon passage of said bits and said splitting means through a workpiece and including resilient means supported on said workpiece supporting frame for displaceable engagement with a workpiece upon the same being engaged by said side clamping means, said resilient means defining an opening aligned with the path of travel of said bits and said splitting means and supporting the exterior surface of the workpiece against splitting outside the outline configuration of the mortise.

5. Apparatus according to claim 1 further comprising:

workpiece discharging means mounted on said workpiece supporting frame and operable for discharging a workpiece from said cradle means for removal from said apparatus.

6. Apparatus according to claim 1 wherein each of said bits includes a tapered thread portion and an abutment shoulder and said bit mounting means comprises:

a cutting head subframe, and

a pair of stub shafts mounted in said subframe for rotation about parallel spaced axes and each having a mating tapered threaded portion and an abutment shoulder for coupling said first and second bits thereto with the respective wing portions positioned in said predetermined angular relationship and for rotation free of interference one with the other.

7. Apparatus according to claim 6 wherein said bit driving means comprises:

a motive force means operatively connected to one of said stub shafts for driving said one shaft in rotation, and

a pair of gears each secured to one of said stub shafts and in meshing engagement one with another.

8. Apparatus for mortising elnogate spilttable material workpieces such as wooden fence posts comprising: an elongate supporting frame including workpiece cradle means for receiving an elongate workpiece with the longitudinal axis thereof generally parallel to the longitudinal axis of said supporting frame,

an elongate mortising head frame normally positioned in predetermined spaced relation above said cradle means,

actuation means for effecting relative movement of said mortising head frame downwardly and upwardly toward and away from said cradle means,

anti-splintering means for avoiding workpiece splitting during mortising and including a plurality of resilient means supported on said supporting frame adjacent said cradle means and underlying said mortising frame for displaceable engagement with a workpiece, each of said resilient means defining an opening generally corresponding in outline with a respective mortise to be formed in the workpiece and supporting the lower exterior surface of the workpiece against splitting outside the outline configuration of such respective mortise, and

a plurality of mortise cutting heads mounted on said mortising frame for adjustable spaced positioning therealong and for forming a corresponding plurality of pa pa mo tis s in a wo kpiece su orted in said cradle means upon engagement therewith as said frames move toward each other, each of said cutting heads comprising:

first and second boring bits having respective cutting wing portions each of a predetermined radius for describing respective circles of predetermined diameters upon rotation of said bits about the longitudinal axes thereof and said bits also having respective shank portions of reduced size relative to said wing portions,

means mounting said first and second bits for rotation with said longitudinal axes thereof parallel and spaced apart a predetermined distance less than the sum of said radii, said mounting means securing said bits with said wing portions in a predetermined angular relationship,

means for driving said first and second bits in rotation about said longitudinal axes thereof and for maintaining a predetermined angular phase relationship between said wing portions so that said first and second bits rotate free of interference one with the other while said wing portions describe overlapping circles, and

means positioned adjacent said shank portions of said bits for splitting generally triangular cusps lying outside and immediately adjacent overlapping circles described by said bits from a workpiece, said splitting means cooperating with said first and second 'bits to form an elongate mortise having rounded ends.

9. Apparatus for forming elongate mortises in splittable materials such as wood and the like comprising:

first and second boring bits having respective cutting Wing portions each of a predetermined radius for describing respective circles of predetermined diameters upon rotation of said bits about the longitudinal axes thereof and said bits also having respective shank portions of reduced size relative to said wing portions,

means mounting said first and second bits for rotation with said longitudinal axes thereof parallel and spaced apart a predetermined distance less than the sum of said radii, said mounting means securing said bits with said wing portions in a predetermined angular relationship,

means for driving said first and second bits in rotation about said longitudinal axes thereof and for maintaining a predetermined angular phase relationship between said wing portions so that said first and second bits rotate free of interference one with the other while said wing portions describe overlapping circles, and

means fixed adjacent said shank portions of said bits and including a chisel portion spaced inwardly of said circles described by said boring bit wing portions and lines tangent to and joining said circles for splitting generally triangularcusps lying outside and immediately adjacent overlapping circles described by said bits from a workpiece, said splitting means cooperating with said first and second bits to form an elongate mortise having rounded ends.

10. Apparatus according to claim 9 wherein each of said bits includes a tapered threaded portion and an abutment shoulder and said stub shaft coupling means comprises a mating tapered threaded portion and an abutment shoulder.

11. Apparatus according to claim 9 wherein said bit driving means comprises:

a motive force means operatively connected to one of said stub shafts for driving said one shaft in rotation, and

a pair of gears each secured to one of said stub shafts and in meshing engagement one with another.

References Cited UNITED STATES PATENTS 502,120 7/1893 Hicks 144-78 517,906 4/1894 Weldon a- 144'-78 658,782 10/1900 Kellogg 1441 10 X 3,389,729 6/1968 Macala 145-605 DONALD R. SCHRAN, Primary Examiner US. Cl. X.R. 14560.5 

